---
title: System Design
description: Notes for system design interviews — how to scope a problem, size it, and pick the parts that carry the load.
icon: network
sidebar:
  label: Overview
---

## How an interview runs

<Steps>
  <Step title="Requirements">
    Pin down the functional requirements (what the system does) and the non-functional ones (latency, availability, consistency, scale) before drawing anything.
  </Step>
  <Step title="Estimates">
    Size the traffic, storage and bandwidth with back-of-the-envelope numbers, so later choices have a reason.
  </Step>
  <Step title="API and data model">
    Define the endpoints and the entities they read and write.
  </Step>
  <Step title="High-level design">
    Draw the request path end to end: clients, load balancers, services, caches, stores and queues.
  </Step>
  <Step title="Deep dives">
    Take the hardest part (a hot key, fan-out, a consistency guarantee) and work through its tradeoffs.
  </Step>
</Steps>